1. Field of the Invention
The present invention relates to linear actuator technology and more particularly, to improved structure of linear actuator, which has a gear shaft of a gear set of the actuator thereof supported in a one-way bearing and a thrust bearing, so that when a driver drives the gear set to rotate a lead screw in moving a retractable tube assembly between an extended position and a received position, the thrust bearing mates with the one-way bearing to bear an axial thrust load, preventing actuator damage and enhancing structural stability.
2. Description of the Related Art
Many different types of linear actuators with different mechanical and transmission designs are known for use in medical or home beds, massage chairs, fitness machines, rehabilitation equipments, door/window openers, lifting mechanisms and many other electrically controllable displacement devices for elevation or angular position adjustment. During the operation of the motor in a conventional linear actuator, a linked retractable tube is moved between an extended position and a received position to achieve elevation or angular position adjustment.
Commercial linear actuators commonly use a motor to drive a worm in rotating a worm gear and a lead screw, moving a retractable tube linearly to lift or lower a coupled link or bracket. However, during the operation of the worm to rotate the worm gear and the connected lead screw in moving the linked retractable tube, the torsional force thus generated is large. When stopping the actuator, the load can cause the lead screw to rotate in the reversed direction, and the retractable tube (or external apparatus) can fall suddenly, causing an accident. In order to prevent this problem, a brake can be added to the actuator to lock the actuator when it is stopped. Further, if the linear actuator bears an impact due to a sudden change in load or any other factor, a large axial thrust load and high impact load will be given to the retractable tube against the lead screw, leading to actuator damage. An improvement in this regard is desired.